Hi John
Perhaps you should do some research before making any comment. Over the years there have been many efforts at sails but the first proper sail designed specifically for kayak paddling are the Flat Earth sails designed by the late Mick MacRobb who sadly passed away as he was just becoming successful with his sails.
See a link below for your perusal but you are well off thmark......seakayakphoto.blogspot.com

Hi Roger
Thanks for the link and the guidance on the phone this eve.
As for 'cheating' I'm with Justine Curgenven quoting from her blog about her Aleutian trip with Sarah Outen...
"A few people have made comments that we somehow aren’t kayaking if we are using sails. Or suggested that it’s cheating or against the rules. We don’t really have any rules and if it makes us quicker and therefore safer in this remote, windy, cold, unpredictable environment then I’m all for it! We are still paddling but the sails make us quicker in certain conditions, much like a longer, sleeker kayak would or even a rudder."

I purchased a used Venture Scout Kayak sail from Jon Hynes. Find it a bit fiddly, but need to give it more practice and push a little harder. I've only been out with it twice in gentle conditions. It attaches to the deck and my paddle and along with the skudder I manage a bit of butt clenching sailing